-LRB- CNN -RRB- -- A rebel group in the Democratic Republic of Congo killed at least 321 civilians and abducted 250 others -- including at least 80 children -- in a previously unreported rampage late last year , Human Rights Watch said in a report released Saturday .

The Lord 's Resistance Army -LRB- LRA -RRB- carried out the brutal campaign in northeastern Congo over four days in December , the report said .

LRA forces attacked at least 10 villages from December 14 to 17 , killing and abducting hundreds of civilians -- including women and children , according to Human Rights Watch .

LRA combatants tied up villagers in the nation 's remote Makombo area and hacked them to death with machetes or crushed their skulls with axes and heavy wooden sticks , the report said .

Most of those killed were adult men , but at least 13 women and 23 children were among the dead -- including a 3-year-old girl who was burned to death , according to Human Rights Watch .

The LRA also killed those they abducted who walked too slowly or tried to escape , Human Rights Watch said .

According to those who managed to escape , children captured by the LRA were forced to kill other children who had disobeyed the LRA 's rules , the report said . In numerous cases , children were ordered to surround the victim in a circle and take turns beating the child on the head with a large wooden stick until the child died , the report said .

`` The Makombo massacre is one of the worst ever committed by the LRA in its bloody 23-year history , yet it has gone unreported for months , '' said Anneke Van Woudenberg , a senior Africa researcher at Human Rights Watch . `` The four-day rampage demonstrates that the LRA remains a serious threat to civilians and is not a spent force , as the Ugandan and Congolese governments claim . ''

CNN could not independently confirm the massacre .

Human Rights Watch said that the roughly 1,000 United Nations peacekeeping troops in LRA-affected parts of northeastern Congo are insufficient to protect civilians . The peacekeeping force is considering removing some troops from the area under pressure from the Congolese government , a move Human Rights Watch warned against on Saturday .

The U.N. Security Council is planning to visit Congo in mid-April to discuss the peacekeeping force 's plans for withdrawal and the protection of civilians , Human Rights Watch said .

The Congolese government denies that the LRA is still a serious threat in the country , which may have contributed to the absence of reports about the December massacre , Human Rights Watch said .

`` We have been forgotten , '' an 80-year-old Congolese man whose son was killed during the massacre told Human Rights Watch . `` It 's as if we do n't exist . ''

`` The government says the LRA are no longer a problem , but I know that 's not true , '' he said . `` I beg of you , please talk to others about what has happened to us . ''

The LRA is led by self-declared mystic and prophet Joseph Kony , who claims his insurgency -- which began in 1986 -- is aimed at replacing Uganda 's government , led by President Yoweri Museveni , with a democracy based on the Bible 's Ten Commandments .

After being pushed out of Uganda in 2005 , the LRA now operates in the remote border area between southern Sudan , Congo , and Central African Republic . In 2005 , the International Criminal Court issued arrest warrants for senior LRA leaders for crimes they committed in northern Uganda , but those indicted remain at large .

The two commanders who perpetrated the December massacre report to one of those indicted leaders , according to Human Rights Watch .

The Makombo massacre is the deadliest documented attack by the LRA since killing sprees around Christmas 2008 left scores of Congolese dead , but dozens of other attacks against civilians have been carried out in other areas in recent months , Human Rights Watch said .

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A rebel group in Congo killed at least 321 civilians , Human Rights Watch said

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The Lord 's Resistance Army abducted 250 others including 80 children , the report said

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LRA forces attacked at least 10 villages from December 14 to 17 , the report claimed

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CNN could not independently confirm reports of the massacre